1. Field
Example embodiments may relate to a method of fabricating a semiconductor device, and more particularly, to a method of fabricating a semiconductor device having gate dielectrics with different thicknesses.
2. Description of the Related Art
Several devices formed on a substrate require different operating voltages. For example, a power voltage is applied directly to an input/output unit or a peripheral circuit region, but the power voltage is dropped to a lower voltage by a voltage drop circuit before the voltage may be applied to a memory device or another peripheral circuit region.
High (or higher) voltage transistors and low (or lower) voltage transistors may be structured differently due to their different operating voltages. For example, each of the transistors has a gate oxide layer with different thicknesses with respect to each other.
To form transistors with gate oxide layers with different thicknesses with respect to each other, a field oxide layer is formed on a substrate and then a thick layer of gate oxide is formed on the entire surface of the substrate. The thick gate oxide layer is etched in a lower voltage region to form a thin gate oxide layer. However, the etching may also etch and recess the field oxide layer around the lower voltage region, which may lead to an excessively lower device isolation breakdown voltage.